Is the relationship shown by the data linear? how can you tell if it is or is not? if so, model the data with an equation.

It is linear. The equation would be: y=2x+19

I got the answer y=2x+21
I got this by counting the difference between the number in the chart
for example: 
-7 +2 =-5, which is the next number in the chart.
so the difference on the X side is +2 and the difference on the y side is +4.
So then we divide 4/2 and we get: 2, so m=2. 
Then to find the x intercept we have to add on to the chart until we get a 0 or a 1 on the x side. (so now you should have 1 on the x side and 21 on the y side) so then we just plug in all these numbers into the equation, y=mx+b
   so the answer should be y=2x+21. 
We know it is linear because the data in the chart can be converted into the equation y=mx+b (I just finished doing this for a gradpoint assignment)